Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 221911 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 311 PM EDT TUE APR 22 2014 .SHORT TERM (TONIGHT AND WEDNESDAY)...
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A BROAD AREA OF LOW PRESSURE OVER THE EASTERN GREAT LAKES WAS CONTINUING TO MOVE EAST THIS AFTERNOON AND EXTENDING OUT OF IT A WEAK COLD FRONT THAT HAD MOVED INTO THE EASTERN OH VALLEY AND WAS DIFFUSE ACROSS CENTRAL TN AND THEN EXTENDED SOUTHWEST INTO CENTRAL LA. AIR MASS WAS BECOMING SOMEWHAT UNSTABLE OVER THE FORECAST AREA BUT ACTIVITY WAS BECOMING WIDELY SCATTERED. MORE CONCENTRATED SHOWERS WERE FORMING NEAR CHATTANOOGA AND TO THE WEST. RAINFALL AMOUNTS HAVE BEEN MOSTLY ONE TENTH OF AN INCH OR LESS SO FAR TODAY AND ONLY ABOUT ONE TENTH AS AN AVERAGE IS EXPECTED THROUGH 00Z OR SHORTLY AFTER SUNSET TONIGHT. TEMPERATURES WERE VARIED IN THE UPPER 50S TO LOWER 60S WHERE SHOWERS WERE OCCURRING TO MID 60S TO LOWER 70S ELSEWHERE. STILL COULD SEE A THUNDERSTORM OR TWO ESPECIALLY SOUTHERN SECTIONS THROUGH EARLY EVENING. OTHERWISE SKIES CLEARING THIS EVENING THEN SUNNY AND COOL AGAIN WEDNESDAY. TEMPERATURES TONIGHT COULD DIP BELOW 40 FOR A FEW HOURS IN THE HIGHER ELEVATIONS OF SOUTHWEST VA AND EASTERN TN BUT NO SIGNIFICANT FROST EXPECTED. WITH SOME COLD AIR ADVECTION WEDNESDAY IT WILL BE BREEZY AND RELATIVE HUMIDITY VALUES MAY DROP TO 20 TO 25 PERCENT BY LATE AFTERNOON. WILL HEADLINE LOW RH AND GUSTY WINDS IN THE FIRE WEATHER FORECAST AND MAY NEED A SPECIAL WEATHER STATEMENT ISSUED EARLY WEDNESDAY. .LONG TERM (WEDNESDAY NIGHT THROUGH TUESDAY)...MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE SYNOPTIC-SCALE PATTERN THROUGH THE EXTENDED PERIOD...AND GENERALLY REVEAL A PROGRESSIVE PATTERN THROUGH EARLY NEXT WEEK. A WEAK COLD FRONT IS PROGGED TO MOVE ACROSS THE TN RIVER VALLEY LATE THURSDAY NIGHT INTO FRIDAY MORNING...BRINGING SCATTERED CONVECTION INTO THE FORECAST AREA AHEAD OF IT. THIS COLD FRONT SHOULD THEN STALL OUT OVER THE DEEP SOUTH ON SATURDAY...AS THE UPPER-LEVEL FLOW BECOMES ZONAL AND PARALLEL TO THE FRONTAL BOUNDARY. THIS FRONTAL BOUNDARY IS THEN PROGGED TO SLOWLY DRIFT NORTHWARD AS A WARM FRONT ON SUNDAY... AND MAY LINGER SOMEWHERE AROUND THE TN RIVER VALLEY THROUGH MONDAY WITH A PROLONGED PERIOD OF CONVECTION POSSIBLE OVER THE FORECAST AREA. A DEEP UPPER-LEVEL TROUGH OVER THE WESTERN U.S. IS THEN PROGGED TO FURTHER AMPLIFY OVER THE SOUTHERN PLAINS ON MONDAY...AND WILL SLOWLY DRIFT EASTWARD EARLY NEXT WEEK...DEVELOPING A STRONG LOW PRESSURE SYSTEM OVER THE LOWER MS RIVER VALLEY. GFS AND ECMWF MODELS DIFFER SOMEWHAT ON THE EXACT TIMING OF THIS SYSTEM...BUT BOTH MODELS AGREE THAT IT WILL BRING STRONG DYNAMICS AND MODERATE INSTABILITY OVER THE FORECAST AREA EARLY NEXT WEEK WITH THE POSSIBILITY OF AN OUTBREAK OF SEVERE STORMS. THUS...WILL BEGIN TO MENTION THIS POSSIBILITY IN THE HAZARDOUS WEATHER OUTLOOK. AS FOR TEMPS...WILL GENERALLY TREND TOWARDS THE GFS NUMBERS THROUGHOUT THE EXTENDED PERIOD...WHICH ARE IN LINE WITH THE ENSEMBLE MEANS.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 47 72 45 78 / 20 0 0 0 KNOXVILLE MCGHEE TYSON AIRPORT, TN 46 70 43 77 / 10 0 0 0 OAK RIDGE, TN 43 70 43 77 / 10 0 0 0 TRI CITIES AIRPORT, TN 40 68 39 75 / 20 0 0 0
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ TD/DMG

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